1. Field of the Invention
This invention relates to a method for fabricating and to the resulting apparatus for implementing a unique Fabry-Perot multiple beam fringe sensor that is suitable to provide an accurate digital representation of a physical parameter.
2. Prior Art
Conventional sensors which are adapted to measure various physical characteristics of a sample typically provide an analog output signal. Consequently, should a digital representation of an output signal be desired, relatively expensive and space consuming analog-to-digital equipment is required. Moreover, such conventional analog sensors are limited in application, because of their inherently large size and slow response time. Moreover, either complex transmission lines or signal conversion apparatus is typically required when the sensor must collect information from a remote sample. Hence, prior art transmission systems that have heretofore been interfaced with sensors of the prior art are relatively expensive to fabricate, are not capable of carrying sufficiently wide bandwidth signals, lack immunity to electro-magnetic and/or electro-static interferences, and require numerous interfacing apparatus.
An example of an optical sensor that is interfaced with a fiber optic transmission system to provide accurate digital representations of a physical parameter from a remote sample can be found in U.S. application Ser. No. 928,223 entitled FIBER OPTIC TEMPERATURE SENSOR, filed July 26, 1978. However, nothing is known in the prior art which shows or suggests the claimed method for fabricating a unique multiple beam fringe sensor that includes a Fabry-Perot cavity, so that the optical characteristics of light transmitted therethrough provide an indication of the change of a physical parameter to be measured. While Fabry-Perot techniques have been previously utilized in non-sensing applications (such as in the construction of a laser), nothing is known in the prior art which applies Fabry-Perot optical principles to an apparatus for sensing physical parameters, such as that disclosed and claimed below.